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### delta u sign

Posted: Sun Jan 22, 2017 9:06 pm
for the delta u equation that states delta u= delta h-p(delta v), does the sign in the middle become plus when there is work being done on the system? Or, is it always minus regardless of work done on or given off?

### Re: delta u sign

Posted: Sun Jan 22, 2017 9:22 pm
Yes, from what I know, it does become a positive when work is being done on the system.

### Re: delta u sign

Posted: Mon Jan 23, 2017 12:42 am
Right - this is since the volume decreases (negative $\Delta$V) and corresponds to a change from: - P$\Delta$V to + P$\Delta$V.